1. * White Alder – Alnus rhombifolia
(AL-nus rom-bee-FOH-lee-uh)
Family: Betulaceae (Birch Family)
Native to: Western United States from Baja to British Columbia. In California, much of the state
except the Mojave Desert, including the Santa Monica & San Gabriel Mtns; along stream banks,
canyon bottomlands and gulches to about 7000 ft., often in small stands along permanent streams.
woody tree
mature height: 40-70+ ft.
mature width: 30-40 ft.
Lovely winter-deciduous tree with striking white-gray bark. Fast growing – to 30 ft. in less than a
decade. Leaves alternate, rounded with serrated edges, prominent veins – shiny above. Leaves
on long petioles (stalks) so they quiver in the wind.
May have one or several trunks. Sweet
fragrance. Roots are invasive (water-seeking) and may damage sidewalks/concrete.
Growth characteristics:
Blooms in winter/early spring in our area. Separate male and female flowers on
each tree. Male flowers on drooping branches (catkins); female flowers develop into small, woody
cones < 1 inch long. Wind pollinated. Seeds are small – spread by wind and water.
Blooms/fruits:
Uses in the garden: Usually planted as a lawn tree in large lawns or as a street tree. Provides good
shade – few other plants can grow beneath it when mature.
moist, shady canyons.
Excellent choice for stream banks and
Sensible substitute for: Non-native deciduous trees.
Attracts: Excellent bird habitat: provides cover, nest sites and seeds for food.
Requirements:
Element
Sun
Soil
Water
Fertilizer
Other
Requirement
Full sun to part-shade.
Any local.
Needs regular summer water – Water Zone 2-3 or 3.
Not needed – probably not harmful.
Use an organic mulch (or let leaf mulch accumulate).
Watch for Alder Borers, which can kill trees. Relatively short-lived (to 80 years).
Can prune up to a more open shape.
Management:
Propagation: from seed: fresh seed in fall; 180 day cold-treat stored seed
Plant/seed sources (see list for source numbers): 1, 3, 6, 8, 13, 14
by cuttings: yes
4/30/13
© Project SOUND